Papachristos, D. P. | Search bioRxiv

bioRxiv2026

AgamOBP4-targeted drug repurposing identifies novel mosquito repellent scaffolds

Odorant-binding proteins (OBPs) play central roles in insect chemoreception and represent attractive molecular targets for the discovery of novel behavior-modifying compounds. We report two crystal structures of Anopheles gambiae OBP4: one complexed with the fluorescent probe N-phenyl-1-naphthylamine and a second containing two indole molecules simultaneously bound within the ligand-binding cavity. Structural comparison revealed two binding subsites accommodating the aromatic moieties of 1-NPN or two indole molecules, while identifying Thr58 and Thr70 as key residues in ligand recognition. A structure-based virtual screening campaign was performed against a volatility-filtered library from DrugBank, FooDB, BioNet, and natural-volatiles datasets. Twenty-three ligands were selected for fluorescence competitive binding assays, identifying four AgamOBP4 binders with micromolar affinities (Ki = 2.4-21.8 M). Among them were benzoyl peroxide, an active anti-acne ingredient, Avex-73 (blarcamesine), a clinical-stage drug candidate, and 2-phenylethyl benzoate, a food- and fragrance-associated ester. Additional candidates include O,p'-DDE, a metabolite of the insecticide DDT, and fluorene, a polycyclic aromatic hydrocarbon detected in foods as environmental or processing-derived contaminants. Seven selected compounds were subsequently evaluated against Aedes albopictus in in-vivo behavioral assays, with benzoyl peroxide displaying the highest repellency (RI = 81.8% at 0.2 mg cm-2). AI-based protein-ligand modeling provided insights into ligand recognition and suggested relationships among binding mode, binding affinity, and bioactivity. Collectively, these findings establish the structural basis of ligand recognition by AgamOBP4, highlight the potential of drug-repurposing and food-derived chemical space as sources of next-generation mosquito repellents, and open new opportunities for the development of OBP4-based biosensors for food-quality and environmental monitoring applications.

biochemistry↗

bioRxiv2020

Volatile allosteric antagonists of mosquito odorant receptors inhibit normal odor-dependent behaviors

Odorant-dependent behaviors in insects are triggered by the binding of odorant ligands to the variable subunits of heteromeric olfactory receptors. Previous studies have shown, however, that specific odor binding to ORco, the common subunit of odorant receptor heteromers, may alter allosterically olfactory receptor function and affect profoundly subsequent behavioral responses. Here we report on the identification of several antagonists of the odorant receptor co-receptor of the African malaria vector Anopheles gambiae, AgamORco, in a small collection of natural volatile organic compounds (VOCs) using a relevant insect cell-based screening platform. Because some of the identified antagonists were previously shown to strongly repel Anopheles and Culex mosquitoes, here we examined the bioactivities of the identified antagonists against Aedes, the third major genus of the Culicidae family. The tested antagonists were found to inhibit the function of Ae. aegypti ORco ex vivo and repel Asian tiger, Ae. albopictus, adult mosquitoes. Specific antagonist binary mixtures elicited higher repellency than single antagonists. Binding competition assays suggested antagonist binding to distinct ORco sites as a likely cause for the enhanced repellence of the blends. These findings demonstrate that a simple screening assay may be used for the identification of allosteric modifiers of olfactory-driven behaviors capable of providing enhanced indoor and outdoor protection against multiple mosquito borne infectious diseases.

neuroscience↗